1. Field of the Invention
The present invention relates to broadband antennas for transmission and reception of radio frequency communications in arrays using multiple broadcast and reception streams. More particularly it relates to planar shaped antenna elements which are especially well adapted for cellular telephone communications and which are employable individually or using individual elements integrated into arrays. In use for a multiple-input and multiple-output scheme or MIMO, the formed elements of the array may be closely spaced yet broadcasted and received concurrently without the need for multiplexing. The element and assembled array performs especially well in the 700 Mhz, 900 Mhz, 1710 Mhz, 1800 Mhz, and 1900 Mhz-2100 Mhz frequency ranges. A unique flare angle change at a mid section of the formed aperture in each element, enhances performance in the middle portion of the frequency bands.
2. Background of the Invention
Since the inception of cellular telephones, cellular service providers have had the task of installing a plurality of antenna sites over a geographic area to establish cells for communication with cellular telephones located in the cell. From inception to the current mode of cellular broadcasting and reception, providers have each installed their own plurality of large external cellular antennas for such cell sites. Generally, such antennas are or cable hookup is necessary to provide a television receiver with the required signal strength to provide a perfect picture and sound to the viewer.
In practice, cell sites are grouped in areas of high population density with the most potential users. Because each cellular service provider, has their own system, each such provider will normally have their own antenna sites spaced about a geographic area to form the cells in their respective system.
In suburban areas, the large dipole or mast type antennas must be placed within each cell. Such masts are commonly spaced 1-2 miles apart in suburban areas and in dense urban areas and may be as close as ¼-½ miles apart.
Such antenna sites with large towers and large masts are generally considered eyesores by the public. Because each provider has their own system of cell sites and because each geographic area has a plurality of providers, antenna blight is a common problem in many urban and suburban areas.
The many different service providers employ many different technologies such as GSM and CDMA using industry standards for 3G and 4G (short for 3rd and 4th generation). They also employ these technologies on bandwidths the provider either owns or leases, and which are adapted to the technologies. Consequently, the different carriers tend to operate on different frequencies and since conventional dipole and other cell antennas are large by conventional construction, even where the different providers are positioning sites near each other, they still have their own cell towers adapted to the length and configuration of the large antennas they employ for their systems and which are adapted to their individual broadcast and receiving bands in the RF spectrum.
Since the many carriers and technologies employ different sized, large antennas, even if they wanted to share cell sites and antennas more often, the nature of the antennas used conventionally discourages it. The result being a plethora of antenna sites, some right next to each other, with large ungainly and unsightly antennas on large towers which are aesthetically unpleasing.
In the case of 3G and 4G technologies, data is broadcast in multiple independent RF streams in schemes such as MIMO to communicated data and voice to and from multiple antennas adapted to handle the frequency of each stream. Antennas conventionally must be spaced from each other at least a wavelength of the RF frequency on which they operate to avoid problems with interference. In the case of a broadband antenna with a low end frequency of 700 Mhz this can be at least a 17 inch spacing requirement of each of the plurality of antenna elements from each other. This physical requirement can be overcome using multiplexing of adjacent antennas to turn them off when one antenna is in broadcast mode or using complicated and expensive smart antenna schemes and switching techniques. However, performance lacks and is prone to problems using such techniques. Additionally, physical spacing, if employed, renders the antenna array for multi stream use very large if the lower frequencies are in the 600-800 MHz spectrum.
As such, there is a continuing unmet need for an improved antenna element and a method of cellular antenna tower or node construction which allows for easy formation and configuration of a cellular tower array for two way communications with customers. Such an array should allow for close spacing of the antenna elements of the array and concurrent reception and broadcast by the multiple antennas closely spaced in the array, without complicated switching or multiplexing. Further, such a device should employ individual antenna elements which provide a very high potential for the as-needed configuration for frequency, polarization, gain, direction, steering and other factors desired in a cellular system for the varying servicing requirements of varying numbers of users over a day's time.
Further, such a device should employ a wideband antenna radiator element able to service all of the frequencies employed by the multiple carriers from 700 MHz to 2100 MHz using MIMO or other multiple broadcast and reception data and voice streams without the need for individual antennas for each band. Such a device should also allow one antenna site to service multiple carriers and providers operating in their respective frequency ranges and eliminate the need for many towers virtually in the same position with each servicing a single carrier.